Oversized drop-in TCC regulator valve for worn GM 6L45, 6L50, 6L80 and 6L90 valve bodies; cures no-lockup, converter slip and harsh TCC apply.
A Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro or Corvette with a 6L80 that shudders on light throttle around 40-60 mph, runs a few hundred RPM high at cruise, or bangs the converter clutch on when it locks up often has a worn TCC regulator valve bore, not a bad converter. The Sonnax 104740-46K is a drop-in repair for that bore in the 6L45, 6L50, 6L80 and 6L90. It replaces the factory TCC regulator valve, shuttle valve, end plug and spring with parts made to seal in a worn bore, and it does not require reaming.
In the 6L80 the TCC pressure control solenoid on the TEHCM does not apply the converter clutch directly. It sends a signal pressure to the TCC regulator valve in the lower valve body, and that valve meters line pressure into the converter clutch apply circuit. The TCM then varies the solenoid to control how fast the clutch engages and how much it is allowed to slip. Because the regulator is constantly modulating, it moves back and forth in its bore thousands of times and wears the aluminum casting oval. Once the bore is worn, oil leaks past the valve lands, apply pressure wanders, and the TCM sees slip it cannot correct.
The Sonnax valves have extended spool lands so they ride in the unworn part of the bore, and a lengthened shuttle valve that resists cocking. Both are hardcoat anodized aluminum. Sonnax states the kit restores proper TCC apply in moderately worn bores.
Torque converter shudder on the 6L80 is also caused by worn-out fluid, and GM bulletins list shudder alongside overheating on these units. Our 6L80 common problems guide covers the fluid exchange that should come first.
Start with the fluid. If a fresh Dexron VI exchange cures the shudder, you saved a valve body job. If it comes back, watch commanded versus actual TCC slip on a scan tool at a steady cruise. Electrical codes such as P2763 or P2764 point at the solenoid or TEHCM circuit instead, and the 6L80 shift solenoid symptoms guide explains how to separate a solenoid fault from a hydraulic one. Once the valve body is out, a vacuum test at the TCC regulator bore tells you for certain whether it is leaking.
This kit fits GM 6L45, 6L50, 6L80 and 6L90 six-speed automatics, which covers the 2006-2020 6L80 trucks, SUVs and performance cars including Silverado, Sierra, Tahoe, Suburban, Yukon, Escalade, Camaro and Corvette, plus the 6L90 heavy-duty and 6L45/6L50 applications. It is intended for moderate bore wear. A bore worn badly enough to fail the vacuum test after installation needs Sonnax's oversized ream-in kit instead. If you are unsure which transmission you have, send us the year and VIN. See every part for this unit on our 6L80 parts page.
A 6L80 pan with drain plug and filter makes future fluid changes easy, and if the casting shows wear in other bores, a 2010-19 6L80 valve body may be the better repair.
| Fits | GM 6L45, 6L50, 6L80, 6L90 automatic transmissions |
| Part number | Sonnax 104740-46K |
| Type | Oversized drop-in Zip Valve TCC regulator valve kit |
| Valve material | Hardcoat anodized aluminum |
| Fixes | No TCC apply, converter slip, harsh lockup, overheating |
| Kit contents | TCC regulator valve, shuttle valve, end plug, spring |
| Machining required | None for moderate bore wear |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. The TCC regulator valve is in the lower valve body, which comes out through the pan opening with the vehicle on a lift. You do need to remove the valve body and TEHCM assembly.
It fixes shudder caused by a worn TCC regulator bore. Shudder caused by degraded fluid or a damaged converter clutch will not go away with this kit alone, which is why a fluid exchange is the first test.
No reaming is required for moderate wear. You need basic hand tools and a vacuum tester to verify the repair. Severely worn bores need the oversized ream-in version instead.
Yes. The kit is listed for the 6L45, 6L50, 6L80 and 6L90, which share the TCC regulator valve design.
Yes. Run a Service Fast Learn with a capable scan tool so the TCM relearns clutch and lockup pressures, then drive through several lockup cycles to confirm the slip reading settles.
Dexron VI. Most 6L80 applications have no dipstick, so the level is checked at the fill plug with the fluid at operating temperature.
